Wednesday, May 2, 2007

QUIZ QUEST..

I dont know how to answer a question that gives for example the 3th term and 9th term. Is there any way to find the first term or the difference in terms only by knowing two terms that are not consecutive?
Posted by at

1 comment:

anto said...

I will adress both kinds of formulas separetely:

Arithmetic:
For an arithmetic sequence in which you are given two non consecutive terms and asked to find the formula you have to follow a series of simple steps. The first one is finding how many "jumps" ocurred. In your examle with the 3rd and 9th term, 6 jumps ocurred. As an example lets just say the third term is 6 and the ninth term is 24. Now that you know this you can apply the formula for an arithmetic sequence

Tn = t1 + (n-1)d

In this case d is 7 (number of spaces increased), t1 is the third term (6) and Tn is the ninth term (24).

24 = 6 + 6d
d = 3

Now you try this example:
T8 = 5 T24= 90

Geometric Sequence:
Here the same strategy applies. Lets say we have a sequence with T5 = 7 and T8 = 56.

Tn = T1(r)^(n-1)

Here Tn = 56, T1 = 7 and n equals 4 (8-5+1)

56 = 7r^(3)
8 = r^3
2 = r

Now you try this example:
T2 = 6 T5 = 384

May 3, 2007 at 2:28 PM

Post a Comment

Subscribe to: Post Comments (Atom)